For many decades separation, classification, cleaning and dewatering of fragmented stocks of hard materiial such as stone, aggregate, coal, sand and the like have been accomplished by shaker screen boxes having screen bodies made up of either coarse-woven steel or other metal netting or of relatively thin sheet metal material provided with sieve openings arranged in predetermined sequence or manner. The abrasion and wear from hard material striking the charging surfaces of such sieves, as well as the tumbling and flow of hard material on such surfaces, has caused rapid deterioration of the metal material.
Further corrosion and deformation of the material has shortened the life of such screens. The din and noise from the charging of such screens and the bouncing and tumbling of hard material has been a source of noise pollution.
In the last fifteen years several efforts have been made to lengthen life of such metal screens by applying coatings of somewhat flexible elastic or elastomer material and in several instances whole screen bodies or sectional screen bodies, each providing a multiplicity of sizing apertures, have been employed. Some of these have been supported and reinforced by an underlying mesh of steel, wires or the equivalent. Complicated molding processes have been required for such prior art shaker screens and since a manufacturer is required to make and have available sieves or screens having mesh sizes, sometimes square, sometimes round, sometimes elongate, in as many as a hundred sizes, the original or investment costs of such molds and processing is extremely high. Some prior structures have employed laminations of elastomer sheets vulcanized to metal sheets and some have employed two or more plies of elastomer sheets of large size properly punched or apertured for the sizing required.
It is an object of my invention to provide a very simple segmented screening body adapted for shaker or vibratory box use which, for each mesh or aperture size of classifying desired, requires essentially, in the preferred form, only one precision mold with facilities for quickly cutting portions from the molding to make complementary segments together with facilities for drilling or boring transverse bores through predetermined portions of the components or segments. For mounting and reinforcing said segments or components a plurality of transverse metal wires or equivalent filaments are employed extending through the said bores and beyond the longitudinal edges of the screen for formation of hooks or attachment means to the shaker box or frame. The employment of such complementary-acting relatively thick segments and components provide charging surfaces for the sieve which very substantially reduces the wear; provides a more uniform and gentle bouncing and tumbling of the particulate hard material along the charging surface; avoids corrosion of materials used, eliminates deformation of the charging surface and very substantially limits noise pollution in operation.